Article History
Received: 30 January 2019
Accepted: 31 May 2019
First Online: 19 June 2019
Competing Interests
: A.C.C.S., H.M. and J.R.B. were employees of GlaxoSmithKline at the time of this study, and H.M. and J.R.B. are company shareholders. There are no other financial or non-financial competing interests.